Red River Gorge, KY

Wednesday, October 22, 2014

The Tale of The Bluegrass Savanna-Woodland

Griffith Woods, Kentucky. Photo by J. Cox. Used without permission

The Inner Bluegrass region of Kentucky is an area well known for its gently rolling hills, fertile cropland, bourbon, and Thoroughbred horses. Much of the region is dominated by agriculture and horse pasture land, while Lexington continues to expand its borders into the surrounding landscape. That the region's native biological communities are no longer completely intact is a widely known fact. However, upon closer investigation, it becomes very difficult to say specifically what the local plant communities may have once looked like in the Bluegrass region.

It has been noted time and again that the prominent botanist E. Lucy Braun described the Bluegrass region as the "most anomalous vegetation area in the eastern United States." Many early explorers wrote short depictions of the vegetation that they experienced as they passed through the area. Several of these observations depict great herds of large ungulates, such as bison and elk, grazing on an understory comprised of wild ryes, running buffalo clover, and an abundance of cane found growing in open, park-like savanna-woodlands.

"There are many canebreaks so thick and tall that is is difficult to pass through them. Where no cane grows there is abundance of wild rye, clover, and buffalo grass, covering vast tracts of country, and affording excellent food for cattle. The fields are covered with abundance of wild herbage not common to other countries."

-John Filson, 1784. The Discovery, Settlement, and Present Site of Kentucke

“On the north-west and south-east sides of the Ohio, below the great Kanhaway river, at a little distance from it, are extensive natural meadows, or savannas. These meadows are from 20 to 50 miles in circuit. They have many beautiful groves of trees interspersed as if by art in them, and which serve as shelter for the innumerable herds of buffalo, deer, etc. with which they abound.”

“In all the fertile parts covered by the forests the soil is completely barren; no herbage is seen except a few plants, scattered here and there; and the trees are always far enough apart that a stag may be seen a hundred or a hundred and fifty fathoms off. Prior to the Europeans settling, the whole of this space, now bare, was covered with a species of the great articulated reed, called arundinaria macrosperma, or cane, which is in the woods from three to four inches [check units] diameter, and grows seven or eight feet high...”

The concept of the Bluegrass savanna became widespread after gaining prominence through the research of Dr. Mary Wharton, professor of botany at Georgetown College. Dr. Wharton's work finds its basis in Lucy Braun's supposition that pre-European Inner Bluegrass forests could not have been dense, and were likely open and park-like. In an article published in the September 1980 issue of the journal Castanea, William Bryant and Dr. Wharton along with William Martin and Johnnie Varner found blue ash, bur oak, Shumard oak, and chinquapin oaks in upward of 395 years in age. In particular, they note that the bur oaks are not known to be species of closed canopy forests, which suggests that the forests in the Bluegrass during the mid to late 1700's had relatively open canopies. These pre-European Bluegrass savanna-woodlands would have included a dense herbaceous understory comprising of cane, clover, and cool season grasses such as Elymus spp. They assert that open conditions could have been maintained by large herds of buffalo and other ungulates rather than fire. The loss of this natural disturbance coincides with the displacement of native grasses and forbs by Kentucky bluegrass and fescue around the time of the earliest intensive settlement of the area by Europeans. This viewpoint of the Bluegrass savanna-woodland is best captured by the 1991 book "Bluegrass Land and Life" by Wharton and Barbour. It is also very commonly found in the descriptions of the region found on state agency website such as the Kentucky State Nature Preserves Commission, and in books about Kentuckys biota, such at "Kentucky's Last Great Places" by the late Thomas G. Barnes.

In a 2008 article published in the Journal of Biogeography (PDF), Ryan McEwan and Brian McCarthy present data that calls into question the extent of the Bluegrass savanna prior to European settlement. Using dendrochronology, or the scientific method of dating trees by counting their annual growth rings, these researchers found evidence of very slow growth of these large "savanna indicator" species prior to European settlement. After European settlement, McEwan and McCarthy found that the rings in these savanna indicator trees are wider, perhaps as a result of tree removal by Europeans in the forests of the Bluegrass region which could have released the remnant "savanna" trees from competition for light and increasing their growth rate. Indeed, the very notion of the savanna as a widespread component of the Bluegrass region of Kentucky is questioned by these results.

I have not been able to find any other more recent research on the topic, although Julian Campbell has compiled a great deal of research on his website, which can be found here. It would appear that the issue of pre-European settlement vegetation in the Bluegrass region of Kentucky continues to be something of a controversy - an interesting one that is at the heart of conservation and restoration ecology, and one that bears much more discussion as well as more research!